Wafer level ultrasonic device and manufacturing method thereof

ABSTRACT

A wafer level ultrasonic device includes a composite layer, a first conductive layer, a second conductive layer, a base, a first electrical connection region, and a second electrical connection region. The composite layer includes an ultrasonic element and a protective layer. The ultrasonic element includes a first electrode and a second electrode. The protective layer has a first connecting channel and a second connecting channel respectively corresponding to the first electrode and the second electrode. The first conductive layer and the second conductive layer are respectively in the first connecting channel and the second connecting channel to connect the first electrode and the second electrode. The base includes an opening forming a closed cavity with the protective layer. The first electrical connection region and the second electrical connection region are respectively filled with metal materials to electrically connect the first conductive layer and the second conductive layer.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a) to Patent Application No. 108144395 in Taiwan, R.O.C. on Dec. 4,2019, the entire contents of which are hereby incorporated by reference.

BACKGROUND Technical Field

The present invention relates to an ultrasonic transmission technology,and in particular, to a wafer level ultrasonic device and amanufacturing method thereof.

Related Art

With the development of smartphones and application programs, anincreasing scope of individual life is covered. For example, smartphonesare widely applied to mobile payment, electronic keys, and the likenowadays. A large amount of important individual information is storedin the smartphone. Therefore, once the smartphone is missing, theinformation is likely to be stolen, resulting in a great loss.

Therefore, in addition to setting a password generally, many functionssuch as face recognition, iris recognition, and fingerprint recognition,which use a personal feature to assist in encryption, have beendeveloped. Fingerprint recognition is used most commonly at present,which, however, still has the problem of inaccurate recognition.

In the current fingerprint recognition technology, a finger touches anupper cover of an ultrasonic module or a screen protective layer of asmart electronic device; the ultrasonic module sends an ultrasonicsignal to the finger and receives a strength of the ultrasonic signalreflected by peaks and roughs of the fingerprint, so that thefingerprint can be recognized. However, the ultrasonic signal of theultrasonic module may be transmitted to an area not in contact with thefinger through a medium. In this case, the reflected ultrasonic signalreceived by the ultrasonic module may not necessarily be reflected bythe finger. Therefore, it is difficult to recognize the fingerprint.

SUMMARY

It should be understood that, when an element is referred to as being“connected to” another element, it may indicate that the element isdirectly connected to the another element, or there is a middle element.

In addition, it should be understood that although terms such as“first”, “second”, and “third” in this specification may be used fordescribing various elements, components, areas, or parts, the elements,components, areas, or parts are not limited by such terms. The terms areonly used to distinguish one element, component, area, or part fromanother element, component, area, or part.

In addition, terms such as “on”, “below”, “top”, and “bottom” are usedfor describing a relative relationship between one element and anotherelement. It should be understood that such relative terms are intendedto encompass different orientations of the device in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, an element described as being “below” anotherelement will then be “above” the other element.

To solve the foregoing problems, a wafer level ultrasonic device isprovided herein, including a composite layer, a first conductive layer,a second conductive layer, a base, a first electrical connection region,and a second electrical connection region. The composite layer includesan ultrasonic element and a protective layer, the ultrasonic elementincludes a first electrode and a second electrode, and the firstelectrode is not connected to the second electrode. The protective layercovers the ultrasonic element and is provided with a first connectingchannel and a second connecting channel, one end of the first connectingchannel corresponds to the first electrode, and one end of the secondconnecting channel corresponds to the second electrode. The firstconductive layer is in the first connecting channel and is electricallyconnected to the first electrode, and a part of the first conductivelayer is exposed to the protective layer. The second conductive layer isin the second connecting channel and is electrically connected to thesecond electrode, and a part of the second conductive layer is exposedto the protective layer. The base is connected to the protective layer,and includes an opening. The opening forms a closed cavity with theprotective layer. The first electrical connection region is filled witha metal material to be electrically connected to the first conductivelayer. The second electrical connection region is filled with a metalmaterial to be electrically connected to the second conductive layer.

In some embodiments, the ultrasonic element includes a firstpiezoelectric layer, the first electrode, a second piezoelectric layer,and the second electrode. The first electrode is on the firstpiezoelectric layer, the second piezoelectric layer is on the firstelectrode, the second electrode is on the second piezoelectric layer,and the second piezoelectric layer and the second electrode do not coverthe first electrode completely.

In more detail, in some embodiments, the protective layer includes afirst protective layer and a second protective layer. The firstprotective layer covers the ultrasonic element, and exposes a part ofthe first electrode and a part of the second electrode. The firstconductive layer and the second conductive layer are on the firstprotective layer, and are connected to the first electrode and thesecond electrode respectively. The second protective layer covers thefirst conductive layer, the second conductive layer, and the firstprotective layer, and exposes a part of the first conductive layer and apart of the second conductive layer.

In some embodiments, the ultrasonic element includes a first ultrasonicunit and a second ultrasonic unit. The first ultrasonic unit includesthe first piezoelectric layer and the first electrode, the firstpiezoelectric layer covers the first electrode, and the firstpiezoelectric layer is provided with a contact hole, to expose a part ofthe first electrode. The second ultrasonic unit does not overlap thefirst ultrasonic unit in a direction perpendicular to a substrate. Thesecond ultrasonic unit includes the second piezoelectric layer, a secondcircuit layer, and the second electrode. The second piezoelectric layerand the first piezoelectric layer are in a same layer and are separatedfrom each other. The second circuit layer is covered in the secondpiezoelectric layer. The second circuit layer and the first electrodeare in a same layer and are separated from each other, and the secondelectrode is on the second piezoelectric layer.

Furthermore, in some embodiments, the protective layer includes a firstprotective layer and a second protective layer. The first protectivelayer covers the first ultrasonic unit and the second ultrasonic unit.The first protective layer is provided with a first communicating holeand a second communicating hole. The first communicating hole is incommunication with a contact hole, and the second communicating holeexposes a part of the second electrode. The first conductive layer isfilled into the contact hole and the first communicating hole and isconnected to the first electrode. The second conductive layer is filledinto a part of the second communicating hole and is connected to thesecond electrode. The second protective layer covers the firstconductive layer, the second conductive layer, the first protectivelayer, and the second electrode, and exposes a part of the firstconductive layer and a part of the second conductive layer.

In more detail, in some embodiments, the first piezoelectric layerincludes a first bottom piezoelectric layer and a first toppiezoelectric layer. The first electrode is on the first bottompiezoelectric layer, and is covered by the first top piezoelectriclayer. The first top piezoelectric layer includes the contact hole toexpose a part of the electrode, the second piezoelectric layer includesa second bottom piezoelectric layer and a second top piezoelectriclayer. The second circuit layer is on the second bottom piezoelectriclayer, and is covered by the second top piezoelectric layer. The secondelectrode is on the second top piezoelectric layer.

In more detail, in some embodiments, the first electrical connectionregion and the second electrical connection region are through holespenetrating the base. Furthermore, the wafer level ultrasonic devicefurther includes two bonding pads. The bonding pads are on one side,away from the protective layer, of the base, and are respectivelyconnected to the metal materials in the first electrical connectionregion and the second electrical connection region.

In some other embodiments, the first electrical connection region andthe second electrical connection region are side edges on the base.

In some embodiments, the base is made of glass.

Herein, a manufacturing method of a wafer level ultrasonic device isfurther provided. The method includes: forming an ultrasonic element ona substrate, where the ultrasonic element includes a first electrode anda second electrode that is not connected to the first electrode; forminga first protective layer on the ultrasonic element and the substrate,and forming a first through hole and a second through hole that expose apart of the first electrode and a part of the second electrode; forminga first conductive layer and a second conductive layer on the firstprotective layer, where a part of the first conductive layer is in thefirst through hole and is connected to the first electrode, and a partof the second conductive layer is in the second through hole and isconnected to the second electrode; forming a second protective layer onthe ultrasonic element, the first protective layer, the first conductivelayer, and the second conductive layer; providing a base, and connectingthe base and the second protective layer in a vacuum environment, wherethe base is provided with an opening, and the opening forms a closedcavity with the protective layer; removing the substrate; forming afirst electrical connection region and a second electrical connectionregion on the base, and forming, on the second protective layer, a firstgroove and a second groove that expose a part of the first conductivelayer and a part of the second conductive layer, where the firstelectrical connection region and the second electrical connection regionare in communication with the first groove and the second grooverespectively; and filling the first electrical connection region, thesecond electrical connection region, the first groove, and the secondgroove with metal materials, so that the metal materials are connectedto the first conductive layer and the second conductive layer.

In some embodiments, the step of forming the ultrasonic elementincludes: forming a first piezoelectric material layer, a firstelectrode material layer, a second piezoelectric material layer, and asecond electrode material layer in sequence; and removing parts of thefirst piezoelectric material layer, the first electrode material layer,the second piezoelectric material layer, and the second electrodematerial layer, to form a first piezoelectric layer, the firstelectrode, a second piezoelectric layer, and the second electrode, wherethe second piezoelectric layer and the second electrode expose a part ofthe first electrode.

In some other embodiments, the step of forming the ultrasonic elementincludes: forming the first piezoelectric material layer and the firstelectrode material layer on the substrate in sequence; removing parts ofthe first piezoelectric material layer and the first electrode materiallayer, to form the first bottom piezoelectric layer and the secondbottom piezoelectric layer that are separated from each other and thefirst electrode and the second circuit layer that are separated fromeach other; forming the second piezoelectric material layer and thesecond electrode material layer in sequence, where the secondpiezoelectric material layer covers the first bottom piezoelectriclayer, the second bottom piezoelectric layer, the first electrode, andthe second circuit layer; and removing parts of the second piezoelectricmaterial layer and the second electrode material, to form a first toppiezoelectric layer, a second top piezoelectric layer, and the secondelectrode that are separated from each other, where the first toppiezoelectric layer covers the first bottom piezoelectric layer and thefirst electrode, the second top piezoelectric layer covers the secondbottom piezoelectric layer and the second circuit layer, and the secondelectrode is on the second top piezoelectric layer, to form a firstultrasonic unit and a second ultrasonic unit.

In some embodiments, the step of forming the first electrical connectionregion and the second electrical connection region includes penetratingthe base to form two through holes as the first electrical connectionregion and the second electrical connection region, and removing a partof the protective layer to form the first groove and the second groove.Furthermore, the method further includes: forming two bonding pads onone side, away from the protective layer, of the base, where the twobonding pads are respectively connected to the metal materials in thefirst electrical connection region and the second electrical connectionregion.

In some embodiments, the step of forming the first electrical connectionregion and the second electrical connection region includes removingedges of the base and the protective layer to form the first electricalconnection region and the second electrical connection region.

Based on the foregoing, by using the closed cavity between the base andthe protective layer, the speed of ultrasonic transmission throughvacuum and a general medium changes obviously. Therefore, a transferdirection of a signal can be clearly distinguished. Furthermore, becausea propagation direction of an ultrasonic signal may be recognizedclearly, functions such as gesture sensing may be further provided, andcan be applied to a tablet and a television with a large size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a first embodiment.

FIG. 2 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a second embodiment.

FIG. 3 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a third embodiment.

FIG. 4 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a fourth embodiment.

FIG. 5A to FIG. 5I are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe first embodiment.

FIG. 6A to FIG. 6B are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe second embodiment.

FIG. 7A to FIG. 7K are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe third embodiment.

FIG. 8A to FIG. 8B are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe fourth embodiment.

DETAILED DESCRIPTION

FIG. 1 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a first embodiment. As shown in FIG. 1 , the waferlevel ultrasonic device 1 of the first embodiment includes a compositelayer 15, a first conductive layer 31, a second conductive layer 33, abase 40, a first electrical connection region 51, and a secondelectrical connection region 53. The composite layer 15 includes anultrasonic element 10 and a protective layer 20. The ultrasonic element10 includes a first electrode 121 and a second electrode 123. The firstelectrode 121 is not connected to the second electrode 123. Theprotective layer 20 covers the ultrasonic element 10 and is providedwith a first connecting channel 211 and a second connecting channel 213.One end of the first connection channel 211 corresponds to the firstelectrode 121, and one end of the second connection channel 213corresponds to the second electrode 123. The first conductive layer 31is in the first connecting channel 211 and is electrically connected tothe first electrode 121. The second conductive layer 33 is in the secondconnecting channel 213 and is electrically connected to the secondelectrode 123. Parts of the first conductive layer 31 and the secondconductive layer 33 are exposed to the protective layer 20. The base 40is connected to the protective layer 20. The base 40 includes an opening45, and after the base 40 is connected to the protective layer 20, theopening 45 forms a closed cavity H with the protective layer 20. Thefirst electrical connection region 51 is filled with a metal material 61to be electrically connected to the first conductive layer 31. Thesecond electrical connection region 53 is filled with a metal material63 to be electrically connected to the second conductive layer 33.

In more detail, in the first embodiment, the ultrasonic element 10includes a first piezoelectric layer 111, the first electrode 121, asecond piezoelectric layer 113, and the second electrode 123. The firstelectrode 121 is on the first piezoelectric layer 111. The secondpiezoelectric layer 113 is on the first electrode 121. The secondelectrode 123 is on the second piezoelectric layer 113. The secondpiezoelectric layer 113 and the second electrode 123 do not cover thefirst electrode 121 completely. Herein, “on” indicates a stackingrelationship between elements, but does not indicate an absolutedirection relationship.

The protective layer 20 includes a first protective layer 21 and asecond protective layer 23. The first protective layer 21 covers theultrasonic element 10, and exposes a part of the first electrode 121 anda part of the second electrode 123. The first conductive layer 31 andthe second conductive layer 33 are on the first protective layer 21, andare connected to the first electrode 121 and the second electrode 123respectively. The second protective layer 23 covers the first conductivelayer 31, the second conductive layer 33, and the first protective layer21, and exposes a part of the first conductive layer 31 and a part ofthe second conductive layer 33. In other words, the first connectingchannel 211 and the second connecting channel 213 respectively provide,between the first protective layer 21 and the second protective layer23, space for receiving the first conductive layer 31 and the secondconductive layer 33 so as to be connected to the first electrode 121 andthe second electrode 123 respectively.

In the first embodiment, the first electrical connection region 51 andthe second electrical connection region 53 are through holes penetratingthe base 40, and correspond to the first conductive layer 31 and thesecond conductive layer 33 respectively. The metal materials 61 and 63are connected to the first conductive layer 31 and the second conductivelayer 33 through the first electrical connection region 51 and thesecond electrical connection region 53. Herein, the first electricalconnection region 51 and the second electrical connection region 53 inthe figure are oblique, but are not limited thereto actually. Inaddition, the wafer level ultrasonic device 1 further includes twobonding pads 70. The bonding pads 70 are on one side, away from theprotective layer 20, of the base 40 separately, and are respectivelyconnected to the metal materials 61 and 63 in the first electricalconnection region 51 and the second electrical connection region 53. Thebonding pads 70 may have a relatively large size, to be connected to acircuit board (not shown in the figure).

Herein, the base 40 may be made of glass. However, this is only anexample, and is not intended for limitation. Other materials, forexample, silicon wafers and quartz, may also be used.

FIG. 2 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a second embodiment. As shown in FIG. 2 , and withreference to FIG. 1 , a main difference between the first embodiment andthe second embodiment is a structure of the base 40. The base 40 of thesecond embodiment is bowl-shaped. A first electrical connection region55A and a second electrical connection region 55B are side edges at thebase 40 and the protective layer 20, and are filled with metal materials65A and 65B in a lump form to be connected to the first conductive layer31 and the second conductive layer 33.

FIG. 3 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a third embodiment. As shown in FIG. 3 , and withreference to FIG. 1 , a main difference between the third embodiment andthe first embodiment is a structure of the composite layer 15. As shownin FIG. 3 , the ultrasonic element 10 of the third embodiment includes afirst ultrasonic unit 10A and a second ultrasonic unit 10B. The firstultrasonic unit 10A includes a first piezoelectric layer 13 and a firstelectrode 141. The first piezoelectric layer 13 covers the firstelectrode 141. The first piezoelectric layer 13 is provided with acontact hole 571, to expose a part of the first electrode 141. Thesecond ultrasonic unit 10B does not overlap the first ultrasonic unit10A in a direction perpendicular to a substrate. The second ultrasonicunit 10B includes a second piezoelectric layer 17, a second circuitlayer 143, and a second electrode 145. The second piezoelectric layer 17and the first piezoelectric layer 13 are in a same layer and areseparated from each other. The second circuit layer 143 is covered inthe second piezoelectric layer 17. The second circuit layer 143 and thefirst electrode 141 are in a same layer and are separated from eachother, and the second electrode 145 is on the second piezoelectric layer17.

In more detail, in the third embodiment, similar to the first embodimentand the second embodiment, the protective layer 20 includes the firstprotective layer 21 and the second protective layer 23. The firstprotective layer 21 covers the first ultrasonic unit 10A and the secondultrasonic unit 10B. The first protective layer 21 is provided with afirst communicating hole 573 and a second communicating hole 575, andthe first communicating hole 573 is in communication with the contacthole 571. The second communicating hole 575 exposes a part of the secondelectrode 145. The first conductive layer 31 is filled into the contacthole 571 and the first communicating hole 573 and is connected to thefirst electrode 141. The second conductive layer 33 is filled into apart of the second communicating hole 575 and is connected to the secondelectrode 145. The second protective layer 23 covers the firstconductive layer 31, the second conductive layer 33, the firstprotective layer 21, and the second electrode 145, and exposes a part ofthe first conductive layer 31 and a part of the second conductive layer33, to be in electrical conduction with the metal materials 61 and 63filled in the first electrical connection region 51 and the secondelectrical connection region 53 in the base 40.

Referring to FIG. 3 again, the first piezoelectric layer 13 includes afirst bottom piezoelectric layer 131 and a first top piezoelectric layer133. The first electrode 141 is on the first bottom piezoelectric layer131, and is covered by the first top piezoelectric layer 133. The firsttop piezoelectric layer 133 includes the contact hole 571 to expose apart of the first electrode 141. The second piezoelectric layer 17includes a second bottom piezoelectric layer 171 and a second toppiezoelectric layer 173. The second circuit layer 143 is on the secondbottom piezoelectric layer 171, and is covered by the second toppiezoelectric layer 173. The second electrode 145 is on the second toppiezoelectric layer 173. Similarly, herein, “top” and “bottom” indicatea mutual relationship of stacking, but not indicate an absolutedirection relationship.

FIG. 4 is schematic cross-sectional view of a wafer level ultrasonicdevice according to a fourth embodiment. As shown in FIG. 4 , the fourthembodiment may be a combination of the structure of the base 40 at alower part of the second embodiment and a structure of an upper halfpart of the third embodiment, and details are not described hereinagain.

FIG. 5A to FIG. 5I are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe first embodiment. As shown in FIG. 5A, the manufacturing method ofthe wafer level ultrasonic device according to the first embodimentincludes: first, forming a first piezoelectric material layer 11A, afirst electrode material layer 12A, a second piezoelectric materiallayer 11B, and a second electrode material layer 12B on a substrate 600in sequence; next, as shown in FIG. 5B, removing parts of the firstpiezoelectric material layer 11A, the first electrode material 12A, thesecond piezoelectric material layer 11B, and the second electrodematerial layer 12B, to form the first piezoelectric layer 111, the firstelectrode 121, the second piezoelectric layer 113, and the secondelectrode 123, where the first electrode 121 is not connected to thesecond electrode 123. Lengths of the second piezoelectric layer 113 andthe second electrode 123 are shorter than those of the firstpiezoelectric layer 111 and the first electrode 121, so that a part ofthe first electrode 121 is exposed, thus completing manufacturing of theultrasonic element 10.

As shown in FIG. 5C, the first protective layer 21 is formed on theultrasonic element 10 and the substrate 600. The first protective layer21 is provided with a first through hole 215 and a second through hole217 that expose a part of the first electrode 121 and a part of thesecond electrode 123. Herein, the first protective layer 21 may bemanufactured by means of lithography, and may be also manufactured bymeans of laser punching after coating. However, the above are onlyexamples, and not intended for limitation.

Then, as shown in FIG. 5D, the first conductive layer 31 and the secondconductive layer 33 are formed on the first protective layer 21. A partof the first conductive layer 31 is in the first through hole 215 and isconnected to the first electrode 121. A part of the second conductivelayer 33 is in the second through hole 217 and is connected to thesecond electrode 123. Similarly, the first conductive layer 31 and thesecond conductive layer 33 may be also manufactured by means oflithography.

As shown in FIG. 5E, the second protective layer 23 is formed on theultrasonic element 10, the first protective layer 21, the firstconductive layer 31, and the second conductive layer 33.

Subsequently, as shown in FIG. 5F, an original structure is reversed,and the base 40 is provided. The base 40 and the second protective layer20 are connected in a vacuum environment. The base 40 is provided withthe opening 45, and the opening 45 forms the closed cavity H with theprotective layer 20. As shown in FIG. 5G, the substrate 600 is removed.

As shown in FIG. 5H, the first electrical connection region 51 and thesecond electrical connection region 53 are formed on the base 40. Thesecond protective layer 23 forms a first groove 231 and a second groove233 that expose a part of the first conductive layer 31 and a part ofthe second conductive layer 33. The first electrical connection region51 and the second electrical connection region 53 are in communicationwith the first groove 231 and the second groove 233 respectively. In thestate of the first embodiment, a punching technology is used. The firstelectrical connection region 51 and the first groove 231 aresubstantially completed by a same punching procedure, and the secondelectrical connection region 53 and the second groove 233 aresubstantially completed by a same punching procedure.

Finally, as shown in FIG. 5I, the first electrical connection region 51,the second electrical connection region 53, the first groove 231, andthe second groove 233 are filled with the metal materials 61 and 63, sothat the metal materials 61 and 63 are connected to the first conductivelayer 31 and the second conductive layer 33. Further, the method furtherincludes forming the two bonding pads 70. The bonding pads 70 are on oneside, away from the protective layer 20, of the base 40, and arerespectively connected to the metal materials 61 and 63 in the firstelectrical connection region 51 and the second electrical connectionregion 53.

FIG. 6A to FIG. 6B are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe second embodiment. The manufacturing method of the second embodimentis roughly the same as FIG. 5A to FIG. 5G of the first embodiment, anddetails are not described herein again. FIG. 6A shows a first electricalconnection region 55A and a second electrical connection region 55Bformed by directly removing parts of edges of the base 40 and theprotective layer 20. In this case, regions of the first conductive layer31 and the second conductive layer 33, which are exposed after theprotective layer 20 is removed, may be treated as the first groove andthe second groove (not shown in the figure). Finally, as shown in FIG.6B, the first electrical connection region 55A and the second electricalconnection region 55B are filled with metal materials 65A and 65B, andthe wafer level ultrasonic device 1 of the second embodiment iscompleted.

FIG. 7A to FIG. 7K are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe third embodiment. As shown in FIG. 7A, first, a first piezoelectricmaterial layer 13A and a first electrode material layer 14A are formedon the substrate 600 in sequence. Next, as shown in FIG. 7B, parts ofthe first piezoelectric material layer 13A and the first electrodematerial layer 14A are removed, to form the first bottom piezoelectriclayer 131 and the second bottom piezoelectric layer 171 that areseparated from each other and the first electrode 141 and the secondcircuit layer 143 that are separated from each other. As shown in FIG.7C, a second piezoelectric material layer 13B and a second electrodematerial layer 14B are formed in sequence. The second piezoelectricmaterial layer 13B covers the first bottom piezoelectric layer 131, thesecond bottom piezoelectric layer 171, the first electrode 141, and thesecond circuit layer 143.

As shown in FIG. 7D, parts of the second piezoelectric material layer13B and the second electrode material layer 14B are removed, to form thefirst top piezoelectric layer 133, the second top piezoelectric layer173, and the second electrode 145 that are separated from each other.The first top piezoelectric layer 133 covers the first bottompiezoelectric layer 131 and the first electrode 141. The second toppiezoelectric layer 173 covers the second bottom piezoelectric layer 171and the second circuit layer 143. The second electrode 145 is on thesecond top piezoelectric layer 173, to form the first ultrasonic unit10A and the second ultrasonic unit 10B. Then, as shown in FIG. 7E, thefirst protective layer 21 is formed on the first ultrasonic unit 10A andthe second ultrasonic unit 10B, and a first through hole (that is, thecontact hole 571 and the first communicating hole 573) and a secondthrough hole (that is, the second communicating hole 575) are form inthe first protective layer 21 and the first top piezoelectric layer 133by an opening technology.

Subsequently, as shown in FIG. 7F, metal materials are formed on thefirst protective layer 21, and parts of the metal materials are removedto form the first conductive layer 31 and the second conductive layer33. A part of the first conductive layer 31 is filled into the contacthole 571 and the first communicating hole 573 and is connected to thefirst electrode 141. A part of the second conductive layer 33 is in thesecond communicating hole 575 and is connected to the second electrode145. As shown in FIG. 7G, the second protective layer 23 is formed onthe ultrasonic element 10, the first protective layer 21, the firstconductive layer 31, and the second conductive layer 33.

As shown in FIG. 7H, 7I, 7J, and 7K, and with reference to FIG. 5F to5I, the closed cavity H is formed by blocking the base 40 in the sameway, the substrate 600 is removed, the first electrical connectionregion 51 and the second electrical connection region 53 are formed bymeans of punching, the metal materials 61 and 63 are then filled, andthe bonding pads 70 are formed.

FIG. 8A to FIG. 8B are stepwise schematic cross-sectional views of amanufacturing method of the wafer level ultrasonic device according tothe fourth embodiment. The manufacturing method of the wafer levelultrasonic device of the fourth embodiment is the same as FIG. 7A to 7Gof the third embodiment in general, and details are not described hereinagain. As shown in FIG. 8A to FIG. 8B, and with reference to FIG. 6A toFIG. 6B, the first electrical connection region 55A and the secondelectrical connection region 55B are also formed by directly removingparts of edges of the base 40 and the protective layer 20; the firstelectrical connection region 55A and the second electrical connectionregion 55B are then filled with the metal materials 65A and 65B; and thewafer level ultrasonic device 1 of the fourth embodiment is completed.

Based on the foregoing, by using the closed cavity H between the base 40and the protective layer 20 of the wafer level ultrasonic device, thespeed of ultrasonic transmission through vacuum and a general mediumchanges obviously. Therefore, a transfer direction of a signal can beclearly distinguished. In addition to fingerprint recognition, functionssuch as gesture sensing may be further provided though a high resolutionof the wafer level ultrasonic device. In addition, a manufacturingprocess is simple, and a manufacturing cost may be reduced greatly.

Although the present invention has been described in considerable detailwith reference to certain preferred embodiments thereof, the disclosureis not for limiting the scope of the invention. Persons having ordinaryskill in the art may make various modifications and changes withoutdeparting from the scope and spirit of the invention. Therefore, thescope of the appended claims should not be limited to the description ofthe preferred embodiments described above.

What is claimed is:
 1. A manufacturing method of a wafer levelultrasonic device, comprising: forming an ultrasonic element on asubstrate, wherein the ultrasonic element comprises a first electrodeand a second electrode that is not connected to the first electrode;forming a first protective layer on the ultrasonic element and thesubstrate, and forming a first through hole and a second through holethat expose a part of the first electrode and a part of the secondelectrode; forming a first conductive layer and a second conductivelayer on the first protective layer, wherein a first conductive part ofthe first conductive layer is in the first through hole and is connectedto the first electrode, and a second conductive part of the secondconductive layer is in the second through hole and is connected to thesecond electrode; forming a second protective layer on the ultrasonicelement, the first protective layer, the first conductive layer, and thesecond conductive layer; providing a base, and connecting the base andthe second protective layer in a vacuum environment, wherein the basehas an opening, and the opening forms a closed cavity with theprotective layer; removing the substrate; forming a first electricalconnection region and a second electrical connection region on the base,and forming a first groove and a second groove on the second protectivelayer, wherein the first groove and the second groove expose a firstconnection part of the first conductive layer and a second connectionpart of the second conductive layer respectively, and the firstelectrical connection region and the second electrical connection regionare in communication with the first groove and the second grooverespectively; and filling the first electrical connection region, thesecond electrical connection region, the first groove, and the secondgroove with a metal material, so that the metal material is connected tothe first conductive layer and the second conductive layer, wherein thestep of forming the ultrasonic element comprises: forming a firstpiezoelectric material layer and a first electrode material layer on thesubstrate in sequence; removing parts of the first piezoelectricmaterial layer and the first electrode material layer, to form a firstbottom piezoelectric layer and a second bottom piezoelectric layer thatare separated from each other, and the first electrode and a secondcircuit layer that are separated from each other; forming a secondpiezoelectric material layer and a second electrode material layer,wherein the second piezoelectric material layer covers the first bottompiezoelectric layer, the second bottom piezoelectric layer, the firstelectrode, and the second circuit layer; and removing parts of thesecond piezoelectric material layer and the second electrode materiallayer, to form a first top piezoelectric layer, a second toppiezoelectric layer, and the second electrode that are separated fromeach other, wherein the first top piezoelectric layer covers the firstbottom piezoelectric layer and the first electrode, the second toppiezoelectric layer covers the second bottom piezoelectric layer and thesecond circuit layer, and the second electrode is on the second toppiezoelectric layer, to form a first ultrasonic unit and a secondultrasonic unit.
 2. The manufacturing method of a wafer level ultrasonicdevice according to claim 1, wherein the step of the forming the firstelectrical connection region and the second electrical connection regioncomprises penetrating the base to form two through holes as the firstelectrical connection region and the second electrical connectionregion, and removing a part of the protective layer to form the firstgroove and the second groove.
 3. The manufacturing method of a waferlevel ultrasonic device according to claim 2, further comprising:forming two bonding pads on one side, away from the protective layer, ofthe base, wherein the two bonding pads are respectively connected to themetal materials in the first electrical connection region and the secondelectrical connection region.
 4. The manufacturing method of a waferlevel ultrasonic device according to claim 1, wherein the step of theforming the first electrical connection region and the second electricalconnection region comprises removing edges of the base and theprotective layer to form the first electrical connection region and thesecond electrical connection region.